Default ConnPool MaxConnections to 5, require min of 2

conn_pool.go

@@ -1,6 +1,7 @@
 package pgx
 
 import (
+	"errors"
 	log "gopkg.in/inconshreveable/log15.v2"
 	"io"
 	"sync"
@@ -8,7 +9,7 @@ import (
 
 type ConnPoolConfig struct {
 	ConnConfig
-	MaxConnections int // max simultaneous connections to use
+	MaxConnections int // max simultaneous connections to use, default 5, must be at least 2
 	AfterConnect   func(*Conn) error
 }
 
@@ -34,6 +35,13 @@ func NewConnPool(config ConnPoolConfig) (p *ConnPool, err error) {
 	p = new(ConnPool)
 	p.config = config.ConnConfig
 	p.maxConnections = config.MaxConnections
+	if p.maxConnections == 0 {
+		p.maxConnections = 5
+	}
+	if p.maxConnections < 2 {
+		return nil, errors.New("MaxConnections must be at least 2")
+	}
+
 	p.afterConnect = config.AfterConnect
 	if config.Logger != nil {
 		p.logger = config.Logger

conn_pool_test.go

@@ -52,6 +52,35 @@ func TestNewConnPool(t *testing.T) {
 	}
 }
 
+func TestNewConnPoolDefaultsTo5MaxConnections(t *testing.T) {
+	t.Parallel()
+
+	config := pgx.ConnPoolConfig{ConnConfig: *defaultConnConfig}
+	pool, err := pgx.NewConnPool(config)
+	if err != nil {
+		t.Fatal("Unable to establish connection pool")
+	}
+	defer pool.Close()
+
+	if n := pool.MaxConnectionCount(); n != 5 {
+		t.Fatalf("Expected pool to default to 5 max connections, but it was %d", n)
+	}
+}
+
+func TestNewConnPoolMaxConnectionsCannotBeLessThan2(t *testing.T) {
+	t.Parallel()
+
+	config := pgx.ConnPoolConfig{ConnConfig: *defaultConnConfig, MaxConnections: 1}
+	pool, err := pgx.NewConnPool(config)
+	if err == nil {
+		pool.Close()
+		t.Fatal(`Expected NewConnPool to fail with "MaxConnections must be at least 2" error, but it succeeded`)
+	}
+	if err.Error() != "MaxConnections must be at least 2" {
+		t.Fatalf(`Expected NewConnPool to fail with "MaxConnections must be at least 2" error, but it failed with %v`, err)
+	}
+}
+
 func TestPoolAcquireAndReleaseCycle(t *testing.T) {
 	t.Parallel()
 
@@ -131,7 +160,7 @@ func TestPoolAcquireAndReleaseCycle(t *testing.T) {
 func TestPoolReleaseWithTransactions(t *testing.T) {
 	t.Parallel()
 
-	pool := createConnPool(t, 1)
+	pool := createConnPool(t, 2)
 	defer pool.Close()
 
 	conn, err := pool.Acquire()
@@ -274,7 +303,7 @@ func TestPoolReleaseDiscardsDeadConnections(t *testing.T) {
 func TestPoolTransaction(t *testing.T) {
 	t.Parallel()
 
-	pool := createConnPool(t, 1)
+	pool := createConnPool(t, 2)
 	defer pool.Close()
 
 	committed, err := pool.Transaction(func(conn *pgx.Conn) bool {
@@ -329,7 +358,7 @@ func TestPoolTransaction(t *testing.T) {
 func TestPoolTransactionIso(t *testing.T) {
 	t.Parallel()
 
-	pool := createConnPool(t, 1)
+	pool := createConnPool(t, 2)
 	defer pool.Close()
 
 	committed, err := pool.TransactionIso("serializable", func(conn *pgx.Conn) bool {